Grafing, or graft-copolymerization, of various fluorinated monomers to olefinic polymers, including polyethylene and ethylene copolymers, is known. Monomers disclosed in the prior art for grafting to polyolefins include certain fluorinated olefins such as perfluoroalkyl (meth)acrylates and perfluoroalkyl vinylether sulfonates and carboxylates. The catalysts used for preparing grafted polyolefins have included free-radical sources such as peroxides and ionizing radiation.
Japanese Patent Kokai No. 2 60911 A discloses the grafting of fluoroalkyl (meth)acrylates to olefinic polymers, including polyethylene and ethylene copolymers, by heating monomer and polymer in the presence of catalysts, such as benzoyl peroxide, in nonaqueous solvents. The weight ratio of olefn polymer to grafted fluoroalkyl monomer is in the range of 50 to 99/1 to 50. The raft copolymers are useful as water and oil repellents.
Japanese Patent Kokai No. 1 289817 A discloses the grafting to polyolefins of fluorine-containing monomers which do not contain an ester group. These polyolefins include polyethylene and poly-1-butene. These fluorinated monomers include te raf iuoroethylene, fuoroethylene, vinyl fluoride and vinylidene fluoride. The grafting is initiated by free-radical initiators such as peroxides, including benzoyl peroxide, or ionizing radiation, optionally in the presence of a solvent. The grafted products contain 1-1000 weight % of fluorinated monomer, based on the amount of polyolefin. The products are oil and water repellent and resistant to hydrolysis.
Japanese Patent Application 58 198535 A discloses cation exchange membranes prepared by electron-radiation grafting of perfluorovinyl ether carboxylic acid monomers, optionally using a monomer-compatible solvent, onto base polymer films, preferably polyethylene film. Disclosed monomers include those of the formula (a) CF.sub.2 .dbd.CX(OCF.sub.2 CFY).sub.1 (O).sub.m (CFY').sub.n A wherein 1 is 0 or 1-3, m is 0 or 1; n is 0 or 1-12; X is F or CF3; Y and Y' are F or perfluoroalkyl having 1-10 carbon atoms; and A includes COF, CO.sub.2 H, CO.sub.2 R.sup.1, CO.sub.2 M and CN; or (b) CF.sub.2 .dbd.CFO(CF.sub.2).sub.n X wherein n is 0-12 and X is CN, COF, CO.sub.2 H, CO.sub.2 R.sup.1 and CO.sub.2 M; R.sup.1 is alkyl having 1-10 carbon atoms, and M is alkali metal or ammonium.
U.S. Pat. No. 4,384,941 discloses an electrolytic cell comprising a cation exchange membrane consisting of polyethylene grafted with a perfluorovinyl ether sulfonate or sulfonic acid monomer. The latter include monomers of the formula CF.sub.2 .dbd.CF[OCF.sub.2 CF(CF3)].sub.1 OCF.sub.2 CF.sub.2 SO.sub.2 Z wherein 1 is 1-3 and Z is OH, F, NH.sub.2, ONH.sub.4 or OM where M is alkali metal. Grafting is induced by ionizing radiation.
U.S. Pat. No. 4,396,727 discloses a cation-exchange membrane comprising a fluorovinyl sulfonic acid monomer which is radiation grafted to polyethylene. Disclosed monomers include those disclosed in the aforementioned U.S. Pat. No. 4,384,941.
U.S. Pat. No. 4,012,303 discloses polymeric membranes useful in electrochemical cells prepared by radiato n grafting of perf luoralkene sulfonyl fluoride monomers such as EQU F(CF.sub.2).sub.x CF.dbd.CFSO.sub.2 F,
where x is 0 or 1-8, onto various polymeric films, including polyethylene.
U.S. Pat. No. 4,548,993 discloses crosslinking of polymers such as polyethylene, ethylene/vinyl acetate copolymers, and ethylene/propylene copolymers for improved rigidity and creep resistance by grafting said polymers with a carboxylic acid at a temperature of at least 170.degree. C., optionally in the presence of a free radical generator such as an organic peroxide, and optionally followed by the addition of a salt-forming base.
U.S. Pat. No. 4,547,474 discloses Friedel-Crafts catalysts comprising C.sub.4 -C.sub.18 fluorinated sulfonic acids and selected higher valency fluorinated Lewis acids such as SbF.sub.5, NbF.sub.5, TaF.sub.5 and AsF.sub.5, supported on chalcidic solids such as fluorinated alumina or alumina-silica. Nafion.RTM. perfluorovinylether sulfonic acid resins are known to be effective acidic catalysts for Friedel-Crafts alkylation reactions, isomerization reactions, and various polymerization reactions. Nafion.RTM. resins are also used commercially as ion-exchange membranes in electrolytic cells.